Sari-e Saqati was the first man to preach in Baghdad on the mystic truths and the Suh “unity”. Most of the Sufi shaikhs of Iraq were his disciples. He was the uncle of Jonaid and the pupil of Ma’ruf-e Karkhi; he had also seen Habib-e Ra’i. To begin with he lived in Baghdad, where he had a shop. Hanging a curtain over the door of his shop, he would go in and pray, performing several rak’as daily in this fashion.
One day a man came from Mount Lokam to visit him. Lifting aside the curtain, he greeted him. “Shaikh So-and-so from Mount Lokam greets you,” he said. “He dwells in the mountains,” commented Sari. “So his efforts amount to nothing. A man ought to be able to live in the midst of the market and be so preoccupied with God, that not for a single instant is he absent from God.”
This is a good point, although it overstates the case, I am curious where you found it? On the one hand every man has the spiritual right to withdraw from human society in order to focus on the acquisition of knowledge of a higher order, on the other this type of withdrawal is not a prerequisite for such knowledge, as is stated here...
"Without going outside, you may know the whole world.
Without looking through the window, you may see the ways of heaven.
The farther you go the less you know."
-From the Tao Te Ching
This is because knowledge of Reality is inherent in our own being, it does not necessarily depend on external circumstances, although they may support or obstruct it as the case may be. This is what I think Crow was getting at, since the ambience of a modern city, with all its ugliness and superficiality is undoubtedly opposed to an insight into the nature of things, whereas the innocent beauty of nature is a suitable support for contemplation. Human art can also provide the necessary support for contemplation if it meets certain criteria.
Getting back to the original point, I would say that despite the fact that a natural setting is more conducive to an understanding of Reality than a modern city, it is still possible to spend most of your life in the latter without being corrupted by it, if you take certain precautions. It is important to note that 'nature' and Reality are not identical terms, nature too is simply a manifestation of a transcendent order which can be known independently of its manifestations, this is what is suggested by both your quote and the one I took from Lao Tsu. It is also why Thomas Aquinas wrote that art should "imitate nature in her manner of operation", rather than simply imitating nature as such, and this also hints at the reason why art can, to some extent, act as a substitute for nature which Crow seemed to suggest in the OP.
Having said all that, I still think that spending a significant amount of time in a wilderness setting will be immensely beneficial for the vast majority of modern people. I try to spend at least one unbroken two week block in such a setting each year, plus frequent overnight or two night trips in my local area. Just because something is not necessary does not mean it is not valuable, and one should keep in mind that not all people, in fact very few, will have the necessary levels of insight and discipline to remain untouched by the superficiality and decadence of modern existence whilst remaining in close proximity to it.